Development documentation

[lampwins]

Currently there is no documentation regarding development testing for napalm-logs. Ideally this should cover the testing methodology (or at least refer to the napalm-automation general topic on this). It should document how new test cases for configured messages should be setup.

[mirceaulinic]

@lampwins as you've already sorted this out, would you be happy to start working on a document under the Development section, say Testing framework?